The goal of this renewal application is to support and develop the world's most comprehensive research resource specializing in the use of the amphibian Xenopus laevis as a multi-faceted experimental platform for biomedical and immunological research and for the benefit of the whole scientific community. Interests and medical relevance of X. laevis are due to the remarkable similarity of its immune system with that of human, the accessibility to experimentation at all developmental stages, as well as the availability of large genetic and genomic resources, invaluable MHC-defined inbred strains and clones of frogs and tools such as lymphoid tumor cell lines, monoclonal antibodies, MHC tetramers and batteries of validated PCR primers for immune-relevant genes. These animals and reagents that are not commercially available need to be preserved, enriched, and made available to the scientific community. As in previous proposals, two major main aims are proposed: (1) Preserving and promoting the X. laevis research resource for immunobiology by keeping on managing and distributing animal stocks and reagents to laboratories in the US and abroad. We will maintain and further optimize the diversity, quality, productivity and welfare of our animals. We will continue to assist, train and inform scientists, students and educators interested in using X. laevis as a research model. We will continue to foster the accessibility and public awareness of the resource by frequently updating our web site by which we disseminate information to the scientific community. We will cultivate communication, networking and interactions with other Xenopus resources in US and in the world. (2) Developing new methodologies and generating new experimental animals and reagents, with the major goal of integrating and exploiting the recent remarkable advance and success of the CRISPR/Cas9- based genome editing technology to generate transgenic (Tg) Xenopus. This has been identified as a priority by the Xenopus community. The specific objectives will be: (i) To adapt the CRISPR/Cas9 system for immune gene loss-of-function by transgenesis; (ii) To develop reagents of high specificity for key immune receptors and factors; (iii)To generate and characterize fluorescent Tg reporter MHC-defined inbred lines and clones; and (iv) To continue developing X. laevis tadpoles for real time intravital microscopy. In addition to maintaining a research platform that is crucial for the Xenopus scientific community, this project promotes the development of new approaches and technologies that can be rapidly and broadly applied for innovative insights into tissue and organ physiology, immunology and developmental biology. The development and application of these tools and technologies will contribute to the efforts of the Xenopus community assisted by the NIH to establish Xenopus as a relevant model for biomedical research.